The goal of this project is to define the role of infection in the pathogenesis of chronic bronchitis and emphysema. A study population of 100 adult patients and 22 normal control subjects will be closely monitored over a 5 year period for episodes of acute respiratory illness and for changes in pulmonary function. Sixty-six such patients and the 22 normal controls have already been so monitored for the past 3 years. Surveillance for acute respiratory illness will be done at weekly intervals. Pulmonary function measurements will be done at 2 month intervals. Appropriate cultures for pathogenic bacteria, fungi, viruses and mycoplasma will be taken during acute illnesses. Such cultures as well as serologic and immunologic studies for infections with these agents will also be done at 2 month intervals. Clinical, physiologic and microbiologic data will be correlated by computer analysis for the interrelation between specific infections and progression of disease.